scholarly journals Quaternized Amphiphilic Block Copolymers as Antimicrobial Agents

Polymers ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 250
Author(s):  
Chih-Hao Chang ◽  
Chih-Hung Chang ◽  
Ya-Wen Yang ◽  
Hsuan-Yu Chen ◽  
Shu-Jyuan Yang ◽  
...  
Keyword(s):  
Antimicrobial Agents ◽  
Growth Efficiency ◽  
Amphiphilic Block Copolymers ◽  
Bacterial Growth Efficiency ◽  
Side Chain ◽  
Single Chain ◽  
Polymer Morphology ◽  
Hemolytic Effect ◽  
Solvent Environment ◽  
Controllable Factor

In this study, a novel polystyrene-block-quaternized polyisoprene amphipathic block copolymer (PS-b-PIN) is derived from anionic polymerization. Quaternized polymers are prepared through post-quaternization on a functionalized polymer side chain. Moreover, the antibacterial activity of quaternized polymers without red blood cell (RBCs) hemolysis can be controlled by block composition, side chain length, and polymer morphology. The solvent environment is highly related to the polymer morphology, forming micelles or other structures. The polymersome formation would decrease the hemolysis and increase the electron density or quaternized groups density as previous research and our experiment revealed. Herein, the PS-b-PIN with N,N-dimethyldodecylamine as side chain would form a polymersome structure in the aqueous solution to display the best inhibiting bacterial growth efficiency without hemolytic effect. Therefore, the different single-chain quaternized groups play an important role in the antibacterial action, and act as a controllable factor.

The effect of energy and nitrogen supply pattern on rumen bacterial growthin vitro

1991 ◽  
Vol 53 (2) ◽  
pp. 165-175 ◽  
Author(s):  
P. H. Henning ◽  
D. G. Steyn ◽  
H. H. Meissner
Keyword(s):  
Bacterial Growth ◽  
Specific Growth ◽  
Growth Efficiency ◽  
Bacterial Growth Efficiency ◽  
Batch Cultures ◽  
Time Zero ◽  
N Supply ◽  
Pulse Dose ◽  
Supply Pattern ◽  
Glucose Supply

AbstractThe effect of energy and nitrogen (N) supply pattern on rumen bacterial growth was investigated in vitro. In experiment 1, glucose was was fed to batch cultures of mixed rumen bacteria according to three patterns namely a pulse dose at time zero (P); even increments at 0·5-h intervals (G) or an intermediate pattern (I), whilst N was supplied in excess. In experiment 2, glucose and N (not in excess) were fed to batch cultures according to four patterns namely glucose and N as pulse doses at time zero, (EPNP); glucose as a pulse dose at time zero and N in 24 even increments at 0·5-h intervals (EPNG); glucose in 24 even increments at 0·5-h intervals and N as a pulse dose at time zero (EGNP) or both glucose and N in 24 even increments at 0·5-h intervals (EGNG). Fermentaton was studied over a 12-h period for both experiments.In experiment 1, bacterial growth efficiency and specific growth rate (39·8,35·5 and 29·9 (g bacterial dry matter (DM) per mol glucose utilized) and 0·33, 0·27 and 0·20 (fraction per h) for treatments P, I, and G respectively) differed significantly between glucose supply patterns. In experiment 2, bacterial growth efficiency and specific growth rate (33·8, 34·7, 25·9 and 22·5 (g baterial DM per mol glucose) and 0·21, 0·18, 0·14 and 0·13 (fraction per h) for treatments EPNP, EPNG, EGNP and EGNG respectively) differed significantly only between glucose supply patterns.It is concluded that the pattern according to which a given amount of energy becomes available affects bacterial growth efficiency, with the fastest supply rate giving the highest efficiency and that, within accepted levels of N supply, synchronization between energy and N availability may be of less importance to bacterial growth efficiency than the energy supply pattern.

scholarly journals Response of heterotrophic and autotrophic microbial plankton to inorganic and organic inputs along a latitudinal transect in the Atlantic Ocean

2010 ◽  
Vol 7 (5) ◽  
pp. 1701-1713 ◽  
Author(s):  
S. Martínez-García ◽  
E. Fernández ◽  
A. Calvo-Díaz ◽  
E. Marañón ◽  
X. A. G. Morán ◽  
...  
Keyword(s):  
Organic Matter ◽  
Atlantic Ocean ◽  
Bacterial Growth ◽  
Heterotrophic Bacteria ◽  
Growth Efficiency ◽  
Bacterial Growth Efficiency ◽  
Organic Nutrient ◽  
Plankton Biomass ◽  
Latitudinal Transect ◽  
Microbial Plankton

Abstract. The effects of inorganic and/or organic nutrient inputs on phytoplankton and heterotrophic bacteria have never been concurrently assessed in open ocean oligotrophic communities over a wide spatial gradient. We studied the effects of potentially limiting inorganic (nitrate, ammonium, phosphate, silica) and organic nutrient (glucose, aminoacids) inputs added separately as well as jointly, on microbial plankton biomass, community structure and metabolism in five microcosm experiments conducted along a latitudinal transect in the Atlantic Ocean (from 26° N to 29° S). Primary production rates increased up to 1.8-fold. Bacterial respiration and microbial community respiration increased up to 14.3 and 12.7-fold respectively. Bacterial production and bacterial growth efficiency increased up to 58.8-fold and 2.5-fold respectively. The largest increases were measured after mixed inorganic-organic nutrients additions. Changes in microbial plankton biomass were small as compared with those in metabolic rates. A north to south increase in the response of heterotrophic bacteria was observed, which could be related to a latitudinal gradient in phosphorus availability. Our results suggest that organic matter inputs will result in a predominantly heterotrophic versus autotrophic response and in increases in bacterial growth efficiency, particularly in the southern hemisphere. Subtle differences in the initial environmental and biological conditions are likely to result in differential microbial responses to inorganic and organic matter inputs.

scholarly journals Synthesis of Fluorinated Amphiphilic Block Copolymers Based on PEGMA, HEMA, and MMA via ATRP and CuAAC Click Chemistry

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Fatime Eren Erol ◽  
Deniz Sinirlioglu ◽  
Sedat Cosgun ◽  
Ali Ekrem Muftuoglu
Keyword(s):  
Block Copolymer ◽  
Block Copolymers ◽  
Amphiphilic Block Copolymers ◽  
Random Copolymers ◽  
Side Chain ◽  
Dipolar Cycloaddition ◽  
Controlled Synthesis ◽  
H Nmr ◽  
Ft Ir ◽  
Click Coupling

Synthesis of fluorinated amphiphilic block copolymers via atom transfer radical polymerization (ATRP) and Cu(I) catalyzed Huisgen 1,3-dipolar cycloaddition (CuAAC) was demonstrated. First, a PEGMA and MMA based block copolymer carrying multiple side-chain acetylene moieties on the hydrophobic segment for postfunctionalization was carried out. This involves the synthesis of a series of P(HEMA-co-MMA) random copolymers to be employed as macroinitiators in the controlled synthesis of P(HEMA-co-MMA)-block-PPEGMA block copolymers by using ATRP, followed by a modification step on the hydroxyl side groups of HEMA via Steglich esterification to afford propargyl side-functional polymer, alkyne-P(HEMA-co-MMA)-block-PPEGMA. Finally, click coupling between side-chain acetylene functionalities and 2,3,4,5,6-pentafluorobenzyl azide yielded fluorinated amphiphilic block copolymers. The obtained polymers were structurally characterized by1H-NMR,19F-NMR, FT-IR, and GPC. Their thermal characterizations were performed using DSC and TGA.

scholarly journals The ‘Relevant’ Stability of Proteins with Equilibrium Intermediates

2002 ◽  
Vol 2 ◽  
pp. 1209-1215 ◽  
Author(s):  
Javier Sancho ◽  
Marta Bueno ◽  
Luis A. Campos ◽  
Juan Fernandez-Recio ◽  
Maria Pilar Iran ◽  
...  
Keyword(s):  
Side Chain ◽  
Practical Issue ◽  
Single Chain ◽  
Native Conformation ◽  
Native State ◽  
Protein Activity ◽  
Overall Stability ◽  
Protein Stabilisation

Proteins perform many useful molecular tasks, and their biotechnological use continues to increase. As protein activity requires a stable native conformation, protein stabilisation is a major scientific and practical issue. Towards that end, many successful protein stabilisation strategies have been devised in recent years. In most cases, model proteins with a two-state folding equilibrium have been used to study and demonstrate protein stabilisation. Many proteins, however, display more complex folding equilibria where stable intermediates accumulate. Stabilising these proteins requires specifically stabilising the native state relative to the intermediates, as these are expected to lack activity. Here we discuss how to investigate the ‘relevant’ stability of proteins with equilibrium intermediates and propose a way to dissect the contribution of side chain interactions to the overall stability into the ‘relevant’ and ‘nonrelevant’ terms. Examples of this analysis performed on apoflavodoxin and in a single-chain mini antibody are presented.

scholarly journals Temporal Variation of Bacterial Respiration and Growth Efficiency in Tropical Coastal Waters

2009 ◽  
Vol 75 (24) ◽  
pp. 7594-7601 ◽  
Author(s):  
Choon Weng Lee ◽  
Chui Wei Bong ◽  
Yii Siang Hii
Keyword(s):  
Temporal Variation ◽  
Bacterial Growth ◽  
Coastal Waters ◽  
Bacterial Production ◽  
Growth Efficiency ◽  
Bacterial Growth Efficiency ◽  
Bacterial Respiration ◽  
Substrate Quality ◽  
Carbon Demand ◽  
Net Heterotrophy

ABSTRACT We investigated the temporal variation of bacterial production, respiration, and growth efficiency in the tropical coastal waters of Peninsular Malaysia. We selected five stations including two estuaries and three coastal water stations. The temperature was relatively stable (averaging around 29.5°C), whereas salinity was more variable in the estuaries. We also measured dissolved organic carbon and nitrogen (DOC and DON, respectively) concentrations. DOC generally ranged from 100 to 900 μM, whereas DON ranged from 0 to 32 μM. Bacterial respiration ranged from 0.5 to 3.2 μM O2 h−1, whereas bacterial production ranged from 0.05 to 0.51 μM C h−1. Bacterial growth efficiency was calculated as bacterial production/(bacterial production + respiration), and ranged from 0.02 to 0.40. Multiple correlation analyses revealed that bacterial production was dependent upon primary production (r2 = 0.169, df = 31, and P < 0.02) whereas bacterial respiration was dependent upon both substrate quality (i.e., DOC/DON ratio) (r2 = 0.137, df = 32, and P = 0.03) and temperature (r2 = 0.113, df = 36, and P = 0.04). Substrate quality was the most important factor (r2 = 0.119, df = 33, and P = 0.04) for the regulation of bacterial growth efficiency. Using bacterial growth efficiency values, the average bacterial carbon demand calculated was from 5.30 to 11.28 μM C h−1. When the bacterial carbon demand was compared with primary productivity, we found that net heterotrophy was established at only two stations. The ratio of bacterial carbon demand to net primary production correlated significantly with bacterial growth efficiency (r2 = 0.341, df = 35, and P < 0.001). From nonlinear regression analysis, we found that net heterotrophy was established when bacterial growth efficiency was <0.08. Our study showed the extent of net heterotrophy in these waters and illustrated the importance of heterotrophic microbial processes in coastal aquatic food webs.

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